A light-converging optical system has an objective lens arranged at a position to be opposite to an optical information recording medium and including at least one plastic lens, and an aberration correcting element provided on an optical path between the light source and the objective lens and structured by two groups of a positive lens and a negative lens both being a plastic lens. At least one of the positive lens and the negative lens has at least one diffractive surface on which a diffractive structure is formed and a total paraxial power of the aberration correcting element has a temperature dependency satisfying a formula of:PT1<PT0<PT2, or PT1>PT0>PT2,where PT0, PT1 and PT2 are the total paraxial power (mm−1) of the aberration correcting element under the temperature of 25° C., −5° C. and 55° C. respectively.
Legal claims defining the scope of protection, as filed with the USPTO.
4. The light-converging optical system of claim 3 , wherein the objective lens is an objective lens structured by two elements in two groups in which a first lens having a positive refractive power and a second lens having a positive refractive power are arranged in this order from the light source side, and wherein one lens including at least the first lens is a plastic lens.
7. The light-converging optical system of claim 6 , wherein the objective lens is a plastic lens structured by one element in one group.
10. The light-converging optical system of claim 9 , wherein the objective lens is an objective lens structured by two elements in two groups in which a first lens having a positive refractive power and a second lens having a positive refractive power are arranged in this order from the light source side, and wherein at least one lens including the first lens is a plastic lens.
14. The light-converging optical system of claim 13 , wherein the objective lens is a plastic lens structured by one element in one group.
16. The light-converging optical system of claim 15 , wherein the objective lens is an objective lens structured by two elements in two groups in which a first lens having a positive refractive power and a second lens having a positive refractive power are arranged in this order from the light source side, and wherein at least one lens including the first lens is a plastic lens.
17. The light-converging optical system of any one of claims 1 , 2 , 9 , and 12 , wherein a prescribed image side numerical aperture necessary for recording and/or reproducing the optical information recording medium is 0.8 or more.
18. The light-converging optical system of any one of claims 1 , 2 , 9 , and 12 , wherein the light source emits a light flux having a wavelength of 550 nm or less.
21. An optical pickup apparatus for recording and/or reproducing an optical information recording medium, comprising: a light source and the light converging optical system of any one of claims 1 , 2 , 9 and 12 for converging a light flux emitted from the light source onto an information recording plane of the optical information recording medium.
22. The optical pickup apparatus of claim 21 , further comprising: an actuator to adjusting changeably a distance between at least two lenses among lenses included in the aberration correcting element in such a way that a spherical aberration generated on each optical surface of the light converging optical system is minimized.
23. An audio and/or image recording apparatus and/or an audio and/or image reproducing apparatus employing the optical pick apparatus of claim 21 .
26. The aberration correcting element of claim 25 , wherein both of the positive lens and the negative lens are a plastic lens and at least one of the positive lens and the negative lens has at least one diffractive structure on which a diffractive structure is formed.
27. The aberration correcting element of claim 25 , wherein one of the positive lens and the negative lens is a plastic lens and the other one is a glass lens.
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January 17, 2003
November 7, 2006
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